diff --git a/src/cc65/codeopt.c b/src/cc65/codeopt.c
index 0a5eacc14..83cd948cc 100644
--- a/src/cc65/codeopt.c
+++ b/src/cc65/codeopt.c
@@ -601,6 +601,7 @@ static OptFunc DOptCmp6	       	= { OptCmp6,   	     "OptCmp6",        	100, 0,
 static OptFunc DOptCmp7	       	= { OptCmp7,   	     "OptCmp7",        	 85, 0, 0, 0, 0, 0 };
 static OptFunc DOptCmp8	       	= { OptCmp8,   	     "OptCmp8",        	 50, 0, 0, 0, 0, 0 };
 static OptFunc DOptCmp9	       	= { OptCmp9,   	     "OptCmp9",        	 85, 0, 0, 0, 0, 0 };
+static OptFunc DOptComplAX1     = { OptComplAX1,     "OptComplAX1",      65, 0, 0, 0, 0, 0 };
 static OptFunc DOptCondBranches1= { OptCondBranches1,"OptCondBranches1", 80, 0, 0, 0, 0, 0 };
 static OptFunc DOptCondBranches2= { OptCondBranches2,"OptCondBranches2",  0, 0, 0, 0, 0, 0 };
 static OptFunc DOptDeadCode    	= { OptDeadCode,     "OptDeadCode",    	100, 0, 0, 0, 0, 0 };
@@ -698,6 +699,7 @@ static OptFunc* OptFuncs[] = {
     &DOptCmp7,
     &DOptCmp8,
     &DOptCmp9,
+    &DOptComplAX1,
     &DOptCondBranches1,
     &DOptCondBranches2,
     &DOptDeadCode,
@@ -1088,6 +1090,7 @@ static unsigned RunOptGroup3 (CodeSeg* S)
        	C += RunOptFunc (S, &DOptStackOps, 3);
         C += RunOptFunc (S, &DOptShift1, 1);
         C += RunOptFunc (S, &DOptShift4, 1);
+        C += RunOptFunc (S, &DOptComplAX1, 1);
        	C += RunOptFunc (S, &DOptSub1, 1);
        	C += RunOptFunc (S, &DOptSub2, 1);
        	C += RunOptFunc (S, &DOptSub3, 1);
diff --git a/src/cc65/coptneg.c b/src/cc65/coptneg.c
index a25556a01..083815e9a 100644
--- a/src/cc65/coptneg.c
+++ b/src/cc65/coptneg.c
@@ -557,3 +557,54 @@ unsigned OptNegAX2 (CodeSeg* S)
 
 
 
+/*****************************************************************************/
+/*                           complax optimizations                           */
+/*****************************************************************************/
+
+
+
+unsigned OptComplAX1 (CodeSeg* S)
+/* Search for a call to complax and replace it by
+ *
+ *      eor     #$FF
+ *
+ * if X isn't used later.
+ */
+{
+    unsigned Changes = 0;
+    unsigned I;
+
+    /* Walk over the entries */
+    I = 0;
+    while (I < CS_GetEntryCount (S)) {
+
+      	/* Get next entry */
+       	CodeEntry* E = CS_GetEntry (S, I);
+
+	/* Check if this is a call to negax, and if X isn't used later */
+       	if (CE_IsCallTo (E, "complax") && !RegXUsed (S, I+1)) {
+
+            CodeEntry* X;
+
+            /* Add replacement code behind */
+	    X = NewCodeEntry (OP65_EOR, AM65_IMM, "$FF", 0, E->LI);
+	    CS_InsertEntry (S, X, I+1);
+
+            /* Delete the call to negax */
+	    CS_DelEntry (S, I);
+
+	    /* We had changes */
+	    ++Changes;
+	}
+
+	/* Next entry */
+	++I;
+
+    }
+
+    /* Return the number of changes made */
+    return Changes;
+}
+
+
+
diff --git a/src/cc65/coptneg.h b/src/cc65/coptneg.h
index 82bd2f39d..f5c36f79f 100644
--- a/src/cc65/coptneg.h
+++ b/src/cc65/coptneg.h
@@ -164,6 +164,22 @@ unsigned OptNegAX2 (CodeSeg* S);
 
 
 
+/*****************************************************************************/
+/*                           complax optimizations                           */
+/*****************************************************************************/
+
+
+
+unsigned OptComplAX1 (CodeSeg* S);
+/* Search for a call to complax and replace it by
+ *
+ *      eor     #$FF
+ *
+ * if X isn't used later.
+ */
+
+
+
 /* End of coptneg.h */
 
 #endif